Snapped rear mounting stud

Discussion in 'Mounting Techniques for Bicycle Motors' started by ORLANDOVROOM, Mar 27, 2017.

  1. ORLANDOVROOM

    ORLANDOVROOM New Member

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    One of my back mounting studs snapped at the face of the crankcase. I tried using an extracting bit with a drill and after that didn't work tried using a dremel to cut a slot so I could use a flat head to back it out. Neither worked and chewed up the opening of the hole pretty good in the process. Any ideas on how to mount it differently or get the bolt out? Maybe get a new crankcase (and if so where)? Give up on life? I removed the other stud next to the broken one in the pic.:-||
     

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  2. Kioshk

    Kioshk Active Member

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    Oh, I've been there! I was fortunate enough to dremel a viable slot to use the flat-head technique. I'm sorry to say that based on the amount of chewed-up metal there your best bet is probably to get a new case. If your drilling skills are good, you MIGHT be able to helicoil it, but that'd probably be nearly as expensive as a case. Another annoying consideration is that these cases differ slightly between manufacturers. It's possible a new case-half may not mate properly with the other original. Being off the road while awaiting parts stinks too. Sorry buddy!
     
  3. ORLANDOVROOM

    ORLANDOVROOM New Member

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    So I've decide that I will drill and tap a new hole next to the messed up one. With the snapped off bolt filling most of the void in the messed up hole, I figure there will be enough solid material around the new hole to give the bolt in the new hole enough strength and support in the case. The two rear mounting studs will be too close together now to go around the bike frame. For that reason I'm going to bolt the studs to a steel plate and secure the engine to the frame at the top and bottom of the plate as shown in the pics. Only real issue I see is the new plate running into the metal coming up next to the 10-tooth sprocket above the good hole on the left. For that reason I will have to grind away part of the side of the plate to make room for that piece of metal that comes up next to the sprocket. Hopefully this works, any tips on drilling into and tapping the casing? Helicoil?
     

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  4. ZipTie

    ZipTie Member

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    I am no machinist but I would think that Helicoil is very unneeded and may even make it weaker. I would just drill and tap into the casting as it was done originally, as long as you can drill and tap a hole that is 3/4" deep or more.
     
  5. ORLANDOVROOM

    ORLANDOVROOM New Member

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    The issue I have when drilling out that hole or trying to extract the bolt is that the hole is so close to the casing wall to the right of the hole. You can see in the original post pic some scuffs from the drill chuck rubbing against it when trying to drill it out/extract it. Extraction bit is relatively short and the hole-drilling bits I used snapped numerous times during drilling, the longer those get the more easily they will snap although I guess I could go up to a bit size so the bit is long/sturdy enough to get the job done. Other obstacle is the bolt that is snapped off in the hole is SOLID steel and its difficult to put the motor in a position where I can really put all my weight and strength on to it to to get through the bolt in there. I am brainstorming some ideas though like putting an angle on the bracket I purposed on the right casing wall side and extending the casing bolt through the casing and bracket and bolting that side of the engine on there. Ill update when I am free from work and school and actually do something.
     

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